You can go for Dual Degree programme (B.Sc and M.Sc) after completing B.tech programme. But I would suggest you to go for Post Graduate programme or Dual Degree programme Joint M.Sc.-Ph.D. Programmes as you are already Graduate. In order to apply for Joint M.Sc Phd or M.Sc programme you can apply IIT JAM Entrance Exam which is conducted for the admission to the postgraduate programmes offered by IIT’s and IISc. Bangalore. If you are interested to go then you can check the eligibility with the given below link.

https://university.careers360.com/articles/jam

If you are intersted to go for Abroad then Admission criteria varies to the country & University also. You need to decide first about the country or University for the admission to the programme.

Let me know if you have any doubt further.

Good Luck!